It is known that power transformers, for example with a power rating of a few MVA and in a voltage range of from, for example, 5 kV to 30 kV or 110 kV, sometimes even up to 170 kV, are also formed as dry-type transformers, wherein in the last-mentioned voltage range, power ratings of 50 MVA and above are also readily possible. During operation of a transformer, lost heat is developed in the electrical windings of said transformer, and this lost heat should be dissipated to the surrounding environment. Therefore, in order to cool such a dry-type transformer, usually at least one cooling channel guided along the axial extent of the winding is developed in order to pass the lost heat out of the winding interior such as through natural air cooling.
In order to increase the cooling effect, the radially inner low-voltage winding can be divided into a plurality of hollow-cylindrical winding segments which are spaced radially apart and are electrically connected in series, and between which a likewise hollow-cylindrical cooling channel is arranged. However, a cooling channel is usually also provided between the low-voltage winding and the high-voltage winding. A radial distance between adjacent winding modules, which ultimately results in a cooling channel, is in this case provided via electrically insulating rectangular profiles or else via so-called “dog-bone” strips.
However, one disadvantage known arrangements can involve the cooling channel, which depending on the electrical boundary conditions, sometimes should be designed to be wider than a normally accepted width based on the cooling cross section because, if specified, a minimum electrical insulation effect can be called for between adjacent winding modules, which is achieved by correspondingly thicker insulation strips. As a result, the transformer winding can become unnecessarily large and the power density of a transformer is correspondingly reduced.